Electrical fuse



11 1927. Oct G. c. OBRIEN ELECTRICAL FUSE Filed July :5, 1925 I Gera/a C 02/7 H TToEA/EY Patented Oct. 11, 1927.

GERALD G. OBRIEN, OF ST. LOUIS, MISSOURI.

ELECTRICAL FUSE.

Application filed July 3, 1925. Serial No. 41,322.

. My invention refers to electrical fuses of either the plug type or cartridge type. The object of my invention is to provide a fuse in which when the filament is burned out, a new filament may be readily replaced at a trifling cost compared to the cost of replacing an entire fuse plug or cartridge. Another object of my invention is the provision of a fuse that indicates to the eye In or the touch of the hand when the fusible filament has been burned out.

My preferred method of construction is indicated in the several figures of the drawings, in which Fig. 1 is a longitudinal section. Fig. 2 is a cross section through Fig. 3 is a'perspective view. In wiring buildings of many rooms and apartments,

it 1s customary to provide a fuse box in which a fuse, either of the cartridge or, plug type, is inserted in the line of each ramlfication of the current-carrying line-to each separate room or to a set of lights. As the wires run through conduits to and are thus hid from view, it often requires skill or experience to locate the fuse that has burned out.

To overcome this objection and make it easy for the inexperienced person to readily J0 detect the dead fuse, I have devised a method by which as soon as a fuse filament is burned out the fact is indicated outside the casing of the plug or cartridge, so that it is plainly visible to the eye or readily apparent to the touch of the hand in the dark.

Another obj ection'to the conventional type fuse is that when the filament-the most delicate and easily destroyed art of the fuse-is burned out, the entire se is of no use .and is thrown away, thus entailing a useless waste of large economic importance, when it is considered that many millions are annually discarded.

To overcome this needless loss, I have devised a renewable filament that canbe readily replaced-by any person without skill or experience, thereby saving the body of the fuse for continuous use.

My preferred construction is identical in principle and application when used with either the plug type or the cartridge type, hence the description and drawings for the plug type will suffice to cover both types.

An outer shell or body 1, of any suitable non-conducting material, is longitudinally hollowed outadapting it to receive a cap 2,

of like material and like general contour, which may be either screw-threaded onto the body 1, but which is referably held in place by means of oppositely. disposed grooves 3, cut into the inner periphery of thebody 1, parallel with the major axis thereof for a short distance and then turned at right angles circumferentially, so as to receive oppositely disposed dowel pins 4 rigidly aflixed in the cap 2.

When the cap 2 is placed in position for the projecting ends of the dowel pins to enter the grooves, the cap is forced. down until the pins reach the bottom of the grooves and by a slight turn of the cap,

the pins enter the lateral grooves and hold the cap firmly in place.

The function of the electric fuse is to maintain a complete circuit under normal current flow and to break the circuit under overcharged conditions. To accomplish this result, a portion of the path of the circuit is narrowed to a point, as indicated at 5, where an overloading of the circuit will fuse or burn in twain the circuit. To accomplish this function, a complete circuit is formed by the various parts and contracts as follows, the current passes through 6, 7 8, 9, 10, 11 and 12.

The rivet .6 firmly inserted in the lower end of the plug by its flat head forms a good contact with the source of current supply and conducts the currentto the connecting spring 7, transmitting it to the hook 8, affixed to the lower end of the cap 2, thence the current flows through the filament 9, through the spring member 10 to the metal conductor 11, through the contact .at 11, to the metal screw-threaded portion 12.

It is obvious that should the magitude of burnt out and needed replacement.

The fuse filament 9 is provided with rectangular identical apertures at each end, adapted to hook onto the inner hooked end the orifice 15, iu which it 15 r of 8 and the inner hooked end of the spring member 10. When the fuse has been burned out, the plug is unscrewed from its socket, the old filament taken out, and a new one put into place with no loss or waste'except the very inexpensive filament.

The cap 2 is knurled about its external periphery and is provided with a downwardly projecting portion 17, the exterior surface of which is of a contour to adapt it to fit into the hollow of the plug, while its interior face 18 is rectilinear and extends downward when in place to a point adjacent the closed end of the plug, thereby providing anchorage for the filament hook 8, and also to insure proper contact between the' hook 8 and the spring contact 7.

It will thus be seen that in order to renew the filament 9, it is only necessary to turn the cap to release the dowels and take out the plug, and by a slight pressure on the top of the indicator 14, the spring 10 is depressed to a point where the filament 9 may be booked in place.

Having fully described my invention and the method of its operation, what I claim as new and useful and desire to secure by Letters Patent is An electric fuse of the class described, comprising a hollow shell of non-conducting material, closed atone end and screw-threaded adapting it to fit a screw-threaded socket, an electric conductor rigidly aflixed in the geometric center of said closed end of said shell adapted to make an electric contact at' Q said hollow shell, an upwardly curved spring rigidly held at one end by said electric conductor and having its upwardly turned end free adapted to contact with and transmit current to ametal strip rigidly attached to a downwardly projecting portion of a cap enclosing the open end of said hollow shell, a fusible metal conductor detachably aflixed at its lower end to said metal strip and detachably aifixed at its upper end to a spring attached to the upper portion of said enclosing cap, said spring being also attached to a downwardly projecting spring adapted to contact with a grounded conductor whereby when said fuse is burned out it may be readily replaced by removing said enclosing cap without removing the body of said hollow shell.

In witness whereof, I have hereunto aflixed my signature this th day of June, 1925.

GERALD c. OBRIEN. 

